Hello,
I am creating virtual machines and set the url of propellor with
& PropellorRepo.hasOriginUrl "https://salsa.debian.org/picca/propellor.git"
I give the old name since I use the 5.6.0 version available in Debian stable.
It systematically fail each time I provision the machine. I discovered that it failed due to a missing git.
so it seems to me that this property should install git before running 
cheers
I've made the property require Git.installed.
I guess this was not noticed because either I was using some other property that also installed git, or I only tried it outside a virtual machine, and so propellor had installed git as part of its process of bootstrapping a host.